Приложение для Android отключается, как только я его открываю?

Question

Приложение представляет собой простой экран входа в систему, который затем отображает зарегистрированные в посещаемости знаки присутствия ..... хотя он никогда не открывается, просто говорится, что это остановилось, и я могу понять, почему! Может ли кто-нибудь помочь понять почему?

Manifest.xml

<?xml version="1.0" encoding="utf-8"?> 
    <manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    package="uk.ac.qub.qubattend" 
    android:versionCode="1" 
    android:versionName="1.0" > 

    <uses-sdk 
     android:minSdkVersion="8" 
     android:targetSdkVersion="19" /> 

    <application 
     android:allowBackup="true" 
     android:icon="@drawable/ic_launcher" 
     android:label="@string/app_name" 
     android:theme="@style/AppTheme" > 
     <activity 
      android:name="uk.ac.qub.qubattend.MainActivity" 
      android:label="@string/app_name" > 
      <intent-filter> 
       <action android:name="android.intent.action.MAIN" /> 

       <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
     </activity> 
     <activity 
      android:name="uk.ac.qub.qubattend.StudentActivity" 
      android:label="@string/title_activity_student" > 
     </activity> 
    </application> 

</manifest> 

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:paddingBottom="@dimen/activity_vertical_margin" 
    android:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    tools:context=".MainActivity" > 

    <TextView 
     android:id="@+id/textView1" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentLeft="true" 
     android:layout_alignParentTop="true" 
     android:layout_marginLeft="49dp" 
     android:layout_marginTop="69dp" 
     android:text="Student Number" 
     android:textAppearance="?android:attr/textAppearanceMedium" /> 

    <EditText 
     android:id="@+id/editText1" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_below="@+id/textView1" 
     android:layout_centerHorizontal="true" 
     android:layout_marginTop="35dp" 
     android:ems="10" 
     android:inputType="textPersonName" > 

     <requestFocus /> 
    </EditText> 

    <TextView 
     android:id="@+id/textView2" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignLeft="@+id/textView1" 
     android:layout_centerVertical="true" 
     android:text="Password" 
     android:textAppearance="?android:attr/textAppearanceMedium" /> 

    <EditText 
     android:id="@+id/editText2" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignLeft="@+id/editText1" 
     android:layout_below="@+id/textView2" 
     android:layout_marginTop="45dp" 
     android:ems="10" 
     android:inputType="textPassword" /> 

    <Button 
     android:id="@+id/button1" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignLeft="@+id/editText2" 
     android:layout_alignRight="@+id/editText1" 
     android:layout_below="@+id/editText2" 
     android:layout_marginTop="42dp" 
     android:text="Login" /> 

    <TextView 
     android:id="@+id/textView3" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentTop="true" 
     android:layout_alignRight="@+id/textView1" 
     android:layout_marginTop="26dp" 
     android:text="" 
     android:textAppearance="?android:attr/textAppearanceMedium" /> 

</RelativeLayout> 

activity_student.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:paddingBottom="@dimen/activity_vertical_margin" 
    android:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    tools:context=".StudentActivity" > 

    <TextView 
     android:id="@+id/textView1" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentLeft="true" 
     android:layout_alignParentTop="true" 
     android:layout_marginLeft="72dp" 
     android:layout_marginTop="71dp" 
     android:text="Attendance" 
     android:textAppearance="?android:attr/textAppearanceLarge" /> 

    <TextView 
     android:id="@+id/att" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignLeft="@+id/textView1" 
     android:layout_below="@+id/textView1" 
     android:layout_marginTop="63dp" 
     android:text="" 
     android:textAppearance="?android:attr/textAppearanceLarge" /> 

</RelativeLayout> 

класс Student

package uk.ac.qub.Student; 

    public class Student { 
    private String StudentId; 
    private String password; 
    private String week1; 
    private String week2; 
    private String week3; 
    private String week4; 
    private String week5; 
    private String week6; 
    private String week7; 
    private String week8; 
    private String week9; 
    private String week10; 
    private String week11; 
    private String week12; 

    public Student(){ 

    } 
    public Student(String StudentId, String password, String week1, 
      String week2, String week3, String week4, String week5, 
      String week6, String week7, String week8, String week9, 
      String week10, String week11, String week12) { 
     this.StudentId = StudentId; 
     this.password = StudentId; 
     this.week1 = week1; 
     this.week1 = week2; 
     this.week1 = week3; 
     this.week1 = week4; 
     this.week1 = week5; 
     this.week1 = week6; 
     this.week1 = week7; 
     this.week1 = week8; 
     this.week1 = week9; 
     this.week1 = week10; 
     this.week1 = week11; 
     this.week1 = week12; 

    } 

    public String getStudentId() { 
     return StudentId; 
    } 

    public void setStudentId(String studentId) { 
     StudentId = studentId; 
    } 

    public String getPassword() { 
     return password; 
    } 

    public void setPassword(String password) { 
     this.password = password; 
    } 
    public String getWeek1() { 
     return week1; 
    } 
    public void setWeek1(String week1) { 
     this.week1 = week1; 
    } 
    public String getWeek2() { 
     return week2; 
    } 
    public void setWeek2(String week2) { 
     this.week2 = week2; 
    } 
    public String getWeek3() { 
     return week3; 
    } 
    public void setWeek3(String week3) { 
     this.week3 = week3; 
    } 
    public String getWeek4() { 
     return week4; 
    } 
    public void setWeek4(String week4) { 
     this.week4 = week4; 
    } 
    public String getWeek5() { 
     return week5; 
    } 
    public void setWeek5(String week5) { 
     this.week5 = week5; 
    } 
    public String getWeek6() { 
     return week6; 
    } 
    public void setWeek6(String week6) { 
     this.week6 = week6; 
    } 
    public String getWeek7() { 
     return week7; 
    } 
    public void setWeek7(String week7) { 
     this.week7 = week7; 
    } 
    public String getWeek8() { 
     return week8; 
    } 
    public void setWeek8(String week8) { 
     this.week8 = week8; 
    } 
    public String getWeek9() { 
     return week9; 
    } 
    public void setWeek9(String week9) { 
     this.week9 = week9; 
    } 
    public String getWeek10() { 
     return week10; 
    } 
    public void setWeek10(String week10) { 
     this.week10 = week10; 
    } 
    public String getWeek11() { 
     return week11; 
    } 
    public void setWeek11(String week11) { 
     this.week11 = week11; 
    } 
    public String getWeek12() { 
     return week12; 
    } 
    public void setWeek12(String week12) { 
     this.week12 = week12; 
    } 



    } 

Основная деятельность

package uk.ac.qub.qubattend; 

import java.util.ArrayList; 

import uk.ac.qub.DBConnection.DBHelper; 
import uk.ac.qub.Student.Student; 


import android.os.Bundle; 
import android.app.Activity; 
import android.content.Intent; 
import android.view.Menu; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.TextView; 

public class MainActivity extends Activity implements OnClickListener { 
EditText username; 
EditText password; 
TextView loginerror; 
Button login; 
ArrayList<Student> studentList; 
static ArrayList<Student> currentStudent; 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    DBHelper db = new DBHelper(this); 
    studentList = (ArrayList<Student>)db.getAllStudents(); 

    username = (EditText)findViewById(R.id.editText1); 
    password = (EditText)findViewById(R.id.editText2); 
    loginerror = (TextView)findViewById(R.id.textView3); 
    login = (Button)findViewById(R.id.button1); 
    login.setOnClickListener(this); 

} 


@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.main, menu); 
    return true; 
} 



@Override 
public void onClick(View v) { 
    String uname = username.getText().toString(); 
    String pass = password.getText().toString(); 

    switch (v.getId()) { 
    case R.id.button1: 
     for(Student s : studentList){ 
      if(s.getStudentId().equals(uname) && s.getPassword().equals(pass)){ 
      Intent i = new Intent(this, StudentActivity.class); 
      currentStudent.add(s); 
      startActivity(i); 
     } else { 
      loginerror.setText("Invalid Login Details"); 
      username.setText(""); 
      password.setText(""); 
     } 

     break;} 

    default: 
     break; 
    } 


} 

} 

StudentActivity класс

package uk.ac.qub.qubattend; 

import java.util.ArrayList; 

import uk.ac.qub.Student.Student; 
import android.app.Activity; 
import android.os.Bundle; 
import android.view.Menu; 
import android.widget.TextView; 

public class StudentActivity extends Activity { 

TextView attendance; 
ArrayList<Student> cstudent; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_student); 
    attendance = (TextView)findViewById(R.id.att); 
    cstudent = (ArrayList<Student>) MainActivity.currentStudent; 
    for (Student s : cstudent) { 
     attendance.setText(s.getWeek1() + "\n" + s.getWeek2() + "\n" 
       + s.getWeek3() + "\n" + s.getWeek4() + "\n" + s.getWeek5() 
       + "\n" + s.getWeek6() + "\n" + s.getWeek7() + "\n" 
       + s.getWeek8() + "\n" + s.getWeek9() + "\n" + s.getWeek10() 
       + "\n" + s.getWeek11() + "\n" + s.getWeek12()); 
    } 

} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.student, menu); 
    return true; 
} 

} 

DBHelper класс

package uk.ac.qub.DBConnection; 

import java.util.ArrayList; 
import java.util.List; 

import uk.ac.qub.Student.Student; 
import android.content.ContentValues; 
import android.content.Context; 
import android.database.Cursor; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteOpenHelper; 

public class DBHelper extends SQLiteOpenHelper { 
// Database Version 
private static final int DATABASE_VERSION = 3; 
// Database Name 
private static final String DATABASE_NAME = "QUBAttendanceDB"; 
// tasks table name 
private static final String TABLE_StudentInfo = "studentinfo"; 
// Table Columns names 
// id column 
private static final String KEY_ID = "StudentId"; 
// question column 
private static final String KEY_PASS = "question"; 
// answer column 
private static final String KEY_WEEK1 = "Week1"; 
private static final String KEY_WEEK2 = "Week2"; 
private static final String KEY_WEEK3 = "Week3"; 
private static final String KEY_WEEK4 = "Week4"; 
private static final String KEY_WEEK5 = "Week5"; 
private static final String KEY_WEEK6 = "Week6"; 
private static final String KEY_WEEK7 = "Week7"; 
private static final String KEY_WEEK8 = "Week8"; 
private static final String KEY_WEEK9 = "Week9"; 
private static final String KEY_WEEK10 = "Week10"; 
private static final String KEY_WEEK11 = "Week11"; 
private static final String KEY_WEEK12 = "Week12"; 

// Database constant 
private SQLiteDatabase dbase; 

/** 
* Method to check the db name and version 
* 
* @param context 
*/ 
public DBHelper(Context context) { 
    super(context, DATABASE_NAME, null, DATABASE_VERSION); 
} 

@Override 
public void onCreate(SQLiteDatabase db) { 
    dbase = db; 
    // Create Table method 
    String sql = "CREATE TABLE IF NOT EXISTS " + TABLE_StudentInfo + " (" 
      + KEY_ID + " TEXT" + KEY_PASS + " TEXT, " + KEY_WEEK1 
      + "TEXT, " + KEY_WEEK2 + "TEXT, " + KEY_WEEK3 + "TEXT, " 
      + KEY_WEEK4 + "TEXT, " + KEY_WEEK5 + "TEXT, " + KEY_WEEK6 
      + "TEXT, " + KEY_WEEK7 + "TEXT, " + KEY_WEEK8 + "TEXT, " 
      + KEY_WEEK9 + "TEXT, " + KEY_WEEK10 + "TEXT, " + KEY_WEEK11 
      + "TEXT, " + KEY_WEEK12 + "TEXT, " + ")"; 
    db.execSQL(sql); 
    // implementing add questions method 
    addAttendance(); 

} 

/** 
* Add Questions Method using Question Object with question, 4 options and 
* correct answer 
*/ 
private void addAttendance() { 
    Student s1 = new Student("40023798", "letmeinhere", "90", "80", "0", 
      "0", "0", "0", "0", "0", "0", "0", "0", "0"); 
    this.addStudent(s1); 

} 

// Checking that existing database table called TABLE_QUEST is dropped 
@Override 
public void onUpgrade(SQLiteDatabase db, int oldV, int newV) { 
    // Drop older table if existed 
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_StudentInfo); 
    // Create tables again 
    onCreate(db); 
} 

/** 
* method for adding a new question into the database 
* 
* @param quest 
*/ 
public void addStudent(Student student) { 
    ContentValues values = new ContentValues(); 
    values.put(KEY_ID, student.getStudentId()); 
    values.put(KEY_PASS, student.getPassword()); 
    values.put(KEY_WEEK1, student.getWeek1()); 
    values.put(KEY_WEEK2, student.getWeek2()); 
    values.put(KEY_WEEK3, student.getWeek3()); 
    values.put(KEY_WEEK4, student.getWeek4()); 
    values.put(KEY_WEEK5, student.getWeek5()); 
    values.put(KEY_WEEK6, student.getWeek6()); 
    values.put(KEY_WEEK7, student.getWeek7()); 
    values.put(KEY_WEEK8, student.getWeek8()); 
    values.put(KEY_WEEK9, student.getWeek9()); 
    values.put(KEY_WEEK10, student.getWeek10()); 
    values.put(KEY_WEEK11, student.getWeek11()); 
    values.put(KEY_WEEK12, student.getWeek12()); 
    // Inserting Row with question 
    dbase.insert(TABLE_StudentInfo, null, values); 
} 

/** 
* Method to move questions in database to an ArrayList 
* 
* @return 
*/ 
public List<Student> getAllStudents() { 
    List<Student> studentList = new ArrayList<Student>(); 
    // Select All Query 
    String selectQuery = "SELECT * FROM " + TABLE_StudentInfo; 
    dbase = this.getReadableDatabase(); 
    Cursor cursor = dbase.rawQuery(selectQuery, null); 
    // looping through all rows and adding to list 
    if (cursor.moveToFirst()) { 
     do { 
      Student student = new Student(); 
      student.setStudentId(cursor.getString(0)); 
      student.setPassword(cursor.getString(1)); 
      student.setWeek1(cursor.getString(2)); 
      student.setWeek2(cursor.getString(3)); 
      student.setWeek3(cursor.getString(4)); 
      student.setWeek4(cursor.getString(5)); 
      student.setWeek5(cursor.getString(6)); 
      student.setWeek6(cursor.getString(7)); 
      student.setWeek7(cursor.getString(8)); 
      student.setWeek8(cursor.getString(9)); 
      student.setWeek9(cursor.getString(10)); 
      student.setWeek10(cursor.getString(11)); 
      student.setWeek11(cursor.getString(12)); 
      student.setWeek12(cursor.getString(13)); 
      studentList.add(student); 
     } while (cursor.moveToNext()); 
    } 
    // return question list 
    return studentList; 
} 

/** 
* Method to Check Database number of rows 
* 
* @return 
*/ 
public int rowcount() { 
    int row = 0; 
    // select all query 
    String selectQuery = "SELECT * FROM " + TABLE_StudentInfo; 
    SQLiteDatabase db = this.getWritableDatabase(); 
    Cursor cursor = db.rawQuery(selectQuery, null); 
    row = cursor.getCount(); 
    return row; 
} 
} 

Answer 1

вы должны проверили logcat, чтобы увидеть, что исключение.

Я предполагаю, что это просто NullPointerError на начальной части. вы можете проследить его из журнала дампа, инициализируя эту переменную перед ее использованием.